The present invention relates generally to the field of data storage using a magnetic tape medium, and more particularly to Linear Tape File System (LTFS) data storage.
The Linear Tape File System (LTFS) is a tape file system that makes it possible to use a tape in the same manner as that of a hard disk without being aware of where and in what order a write is made. Meanwhile, the LTFS is not configured to specify an order in which data blocks are written. More specifically, this means that a stored file that is made up of multiple data blocks, having a certain sequential order, can be stored such that the blocks are scattered about various non-sequential positions on the magnetic tape medium. In this way, the tape medium can be used in a space efficient manner when multiple files, each including multiple blocks, are written to the tape and/or deleted from the tape medium at various times over the operational life of the LTFS. When blocks from a single file are scattered over various physical locations on the tape medium, and a read file operation is performed, the LFTS will have the information it needs to: (i) find the relevant blocks of the file on the tape medium; and (ii) reassemble the data so that the file is provided in the proper order and includes all data of the file that is being read.
State of the art LTFS tapes are configured to include at least two partitions: (i) an index partition containing up to date and previous indexes of the data contents of a magnetic data tape, and (ii) a data partition, itself typically partitioned into a plurality of blocks, purposed for containing the data of the files stored on the magnetic data tape. Some LTFS tapes are configured to periodically store copies of the most up to date index in the data partition during data writing operations, and storing the most up to date version of the index in the index partition once data writing operations are complete.
Tape drives, including tape drives that read LTFS configured magnetic data tapes, typically can only read/write data from/to magnetic data tapes in the direction of from the first data block to the last data block. State of the art tape drives read in this sequence, sometimes called “logical forward.” When a given block is to be read or written to, the tape drive seeks to the beginning of that block and starts the desired data operation, continuing until reaching the end of that block. If further blocks are to be read/written, then the operation continues onto the next block(s).